The present invention relates generally to a Jacquard loom and to a single-leg hook for a double lift open shed Jacquard loom.
In one form of such a machine in which the hooks are controlled by control needles and which includes sets of blades or knives which are movable in opposite directions towards and away from each other, without crossing, by means of lift devices, and a stationary set of arresting knives or blades, as well as a stationary hook rake for guiding the hooks, each hook has two suspension noses or projections which point in the same direction, and a support nose or projection which faces in the same direction. The suspension projections are disposed at the end of a substantially bar-like portion which can be deflected relative to the relatively rigid lower portion of the leg of the hook, which constitutes the predominant part of the leg of the hook.
A hook construction of the general kind outlined above is to be found in German patent specification No. 1 299 258. In that design of hook, the projections thereon are disposed at the ends of a double-armed lever member which is mounted rotatably on the leg of the hook, which is of an overall rigid construction. From a central position in which both projections on the hook can come into engagement with their ends, with the associated blades or knives, the lever member is pivoted about the pivot mounting of the lever member, against the action of a return force, by engagement of the knives or blades into a projection, whereby the other projection is moved to a position outside the region of action of the other blade or knife, and cannot therefore be engaged thereby. The mounting means required to permit the rotational movement of the double-armed lever member constitutes a disadvantage as dust and dirt can penetrate into the mounting means and resinified or gummy grease or oil can result in the lever member becoming unable to rotate. In addition, a separate spring is required in order to produce the return force, thereby to ensure that the lever member takes up a precise central position. By virtue of the action of the one blade or knife, the double-armed lever member must be pivoted beyond the front edge of the leg of the hook by the amount by which the suspension projection projects beyond that front edge, in the central position, so that the other projection is retracted to such an extent that it moves outside the range of action of the knife which moves theretowards. For that reason, the projections on the known hook must be in the form of hook portions which project to a substantial extent. As a result of that construction however, in the phase of operation resulting in engagement with the knife, there is a substantial idle stroke movement or lost motion which has a detrimental effect from the point of view of smoothness of operation.
In another form of hook for a double lift open shed Jacquard machine, of the general kind set forth above, the lower portion of the hook is deflected in the region of intersection of the knives. Thus, in the construction which is disclosed in U.S. Pat. No. 4,060,101, the upper knife box or chest is deflected, which results in a deflection movement of the leg of the hook in the lower region, while in another construction, as disclosed in German laid-open application (DE-OS) No. 23 44 363, the upper portion of a hook has a bulge or curved portion which causes deflection thereof, in the lower region of the hook. However, hooks of that kind are not particularly suitable for high operating speeds because, besides the movement that is necessarily required, the hooks perform uncontrolled movements in the region of intersection, and such movements result in vibration, cause smoothness of operation of the machine to be impaired, and also result in defective control of the assembly, thereby also resulting in defects in the article being produced.